Due to hot-structure temperature limitations, conventional gas turbine engines for fixed wing military aircraft are typically unable to fuel the combustor to stoichiometric fuel/air mixture ratios which results in considerably lower thrust output, and the hot gas exhaust leaving these engines contain large amounts of unused oxygen. Afterburners, not being temperature restricted, are employed to capitalize on the unspent oxygen by burning additionally injected fuel therein, thereby permitting the pilot to selectively generate additional thrust. The additional thrust capacity is typically required for take-off, brief periods of acceleration, supersonic flight and/or critical combat maneuvers.
Conventional afterburners typically include a diffuser, which slows down the hot exhaust gases leaving the gas turbine engine, and a plurality of spray rings or tubes which inject fuel into the passing oxygen-rich exhaust gases. Mixing of the afterburner-injected fuel and the hot exhaust gases is accomplished by high-pressure injection, penetration and atomization. A spark igniter or other suitable ignition source is employed to initiate combustion of the afterburner mixture, while bluff-body flameholders, such as V-shaped gutters that are mounted concentrically around or downstream of a tail cone portion of the diffuser, and their wakes stabilize the flame and sustain self-propagating afterburner combustion. The afterburner diameter is expanded, but not exceeding the main engine diameter, to mitigate thrust loss by decelerating the hot exhaust gases. A variable area nozzle is employed to maximize thrust output for both the lower-temperature exhaust during non-afterburning operation and the high-temperature exhaust during afterburning operation.
As is well known in the art, the capability to afterburn approximately doubles the length of a gas turbine engine and entails a substantial weight penalty. While the weight and packaging issues of an afterburner equipped gas turbine engine are relatively smaller than a turbojet or turbofan engine having a comparable thrust output, there is a need in the art for a relatively more compact and fuel efficient afterburner arrangement.